Or rather, I do not think it means what it is commonly thought to mean.
The polling numbers have changed significantly in response to events, this much is true. But these bounces we've seen do not seem to be showing people changing their minds much - at least, most of the bounce can be accounted for in other ways. Instead, the polls are tracking how much partisan voters want to answer polls. All we can tell is that the race is fairly close, and always has been. The only thing to do is drag our voters out to vote.
The final polling average may very well come close to the actual margin again, but the road to get there has been misleading. It may be that how much partisan voters want to answer polls in September is highly correlated to how the entire voting universe would cast their ballots at that time, but I do not think so.
Why?
I say this because the regional breakdown of the polls was unrealistic during Obama's post-convention bounce, and during the summer, too, for that matter. The debate bounce was mostly caused by a correction of this regional pattern combined with an increase in Conservatives answering thier phones, at least in Daily Kos polling. And finally, response rates are so low that poll respondents are disproportionately highly engaged, politically involved voters. Poll respondents are not representative of voters in general, at least at this stage of the election.
That's not to say polls are useless. Far from it. They still have a decent enough track record for us to be sure the presidential election is close, nationally, and in certain key states. But polls taken weeks and months prior to the election appear to have more error in their margin than we would like to think. And even the averages of polls taken in the final weeks usually miss the margin by more than a point, in races with margins of less than ten points (although this error may be predictable).
Details below.